1. Field of the Invention
This invention relates to an improvement in winding transformers, and more particularly, this invention relates to an improvement in the process of winding rotary transformers featuring bi-directional high level power transmission.
2. Background of the Invention
Windmills, wind turbines, and other wind-actuated power devices may utilize a rotary transformer that comprises one or more rotors and stators positioned at the top of a mast or tower. This paradigm presents special challenges. First, both the stator and especially the rotor must be small in bulk. Also, the rotor rotates at a high rate around a horizontal axis. Yet the windings of both the stator and the rotor must be able to carry large currents; thus it is imperative that effective cooling be provided thereto. Secondly, it is imperative that the rotary transformer be able to withstand extreme weather conditions.
State of the art wind turbine systems use contacting brush and slip ring mechanisms to facilitate power transfer between the stator and the rotor. These are prone to reduced reliability, frequent maintenance problems, and the generation of electrical noise that can interfere with, or damage, sensitive electronics. Oxidation and environmental agents, such as water, ice, and dust, have adverse effects on brush/slip-ring power transmission.
Replacing brush/slip-ring mechanisms with contactless configurations often ameliorate some of the problems associated with operations in environmentally-harsh situations. However, a problem inherent with contactless systems is the generation of high temperatures within the windings. This ultimately leads to reduced power output and eventually, damage to the transformer.
U.S. Pat. No. 7,288,870 (Mitcham, et al. —Oct. 30, 2007) entitled “Stator core” discloses a stator core comprising laminations of low loss stator iron positioned in parallel with laminates of high thermal conductivity material regularly arranged within the core.
U.S. Pat. No. 6,388,548 (Saito, et al. May 14, 2002) discloses a contact-less transformer that includes two disc-shaped ferrite magnetic cores, each disc comprising four quarter sections defining an arc. The quarter sections are closely mated to form the disc, whereby the arcs combine to form one or more continuous circular grooves. Windings are received within the grooves.
A problem with current winding configurations is that wire, when first placed into the grooves of carriers, tend not to stay in place. Specifically, once a wire is unwound from a supply spool and placed in a winding groove, the wire strands do not conform to the smooth curved arcs defined by state of the art winding carriers. This is so because the wire strives to maintain an arcuate shape with a radius of curvature matching that of its supply spool. Nor can the wire be consistently positioned to contact the carrier. Narrowing the winding groove does not always lead to a satisfactory arrangement inasmuch as two wires may come in contact with each other in several places. This would lead to local heat build up and electronic interference. Configuring wire ways to accept only one wire is costly and inefficient, particularly if a high number of windings is desired. Moreover, single-wire wire ways do not provide adequate flexibility when one is laying stiff wires such as the ones one often encounters in rotary transformers.
A need exists in the art for a rotary transformer to, in a contact-less configuration, transfer electrical power at levels in the 1 megaWatt range. The device must operate in extreme environmental conditions (such as high moisture, high particulate environs) and in wide ambient temperature differentials. The device must also facilitate the transfer of heat away from primary and secondary windings so as to optimize operation and longevity and therefore minimize servicing requirements. A need also exists for a manufacturing method to economically produce accurate windings consistently.